Amy,
After two years of procrastination, I finally bought a Dyson. I love it, especially because it has cut my vacuuming time in half.
I did a lot of research so let me share something with you. The differences in the Dyson are down to a couple of things. First, you can either get the regular push or "the ball". The only difference after that is the attachments. For example, the Animal is the same as the All Floors with a couple of exceptions, the color and the attachments it comes with. Of course, because the Animal comes with more attachments, the cost is highter. Make sure you review the attachments to be sure you are not wasting money on tools you may not use. It took me awhile to figure this out as I thought there may be some difference in the strength of the vacuum.
I have two dogs that shed almost constantly. This vacuum is absolutely brilliant in picking up dog hair.
P.S. I just read the post prior to mine. I have to rebut the comment about the Dyson bagless. It is the cleanest to empty that I've ever used and I've had two bagless before my Dyson. I also just hate to have to remember to buy more bags. It also holds more dirt and dog hair than my others did. I do agree that the Dyson is heavy but I guess for me that's okay because I lift weights anyway :+ .